Method of and apparatus for electrotanning.



L. A. GROTH. METHOD OF AND APPARATUS FOR ELECTROTANNING.

APPLICATION FILED OCT. 5. 1914- 1,222,6L

Apr; 17, 1917.

2 S HEETSSHEET I.

Patented L. A. GROTH.

METHOD OF AND APPARATUS FOR ELECTROTANNING.

APPLICATION FILED OCT. 5, I914.

Patented Apr. 17, 1917.

2 sHEETs-sHEET 2. 2/ 5 w I Z DEIEIIIIIILE DECIDE] [155mm UCIIIIDIII 6 4 degrees Baum'.

LORENTZ ALBERT GROTI-I, OF LONDON, ENGLAND.

METHOD OF AND APPARATUS FOR ELECTROTANNING.

Specification of Letters Patent.

Patented Apr. it, 191?.

Application filed October 5, 1914. Serial No. 865,210.

To all whom it may concern:

Be it known that I, LORENTZ ALBERT GRoTH, a subject of Sweden, residing at 10 Gratton road, Kensington West, in the city of London, England, doctor of science and consulting engineer, have invented certain Improvements in Methods of and Apparatus for Electrotanning, of which the following is a specification.

The transfer of matter in liquids, for instance a tannic acid solution, under the influence of the electric current, may take place by 1. Ionic conduction -in which dissolved matter passes as ions, in both directions, and chemical decomposition takes "place at the electrodes.

2. Cataphoresis, which involves the move ment of colloid particles, usually in one direction only, and Without perceptible decomposition; and

3. Electric endosmose in which bodily through a porous Wall.

The addition of electrolyteswill alter the;

concentration of tannic acid lOIlS, decrease the endosmotic movement, and often alter the velocity and sometimes the direction of the cataphoretic movement. Such additions will greatly increase the conductivity of the solution, with the result that the proportion of current employed in the useful work of tannic transference is greatly reduced.

The successful adoption of electricity in tanning depends, more or less, upon how, and by what means it is carried intopractical effect. There are therefore various conditions of an important nature which require different governing adjustments that must be determined in order to enable electrotanning to become of practical and economic value, among which may be mentioned The nature of the interaction that takes place between the gelatin of the hide and the various sterilizing media and tannins employed, not merely under ordinary circumstances but also under the altered conditions caused by the introduction of electricity.

Assume for instance, four tanks in series, the whole system therefore receiving a common electric current, and that the four tanks contain different electrolytes, say ordinary tanning liquors of respectively 1, 2, 3, and

The conditions of current density will not be the same; therefore the results on the liquors as well as on the the liquid or solution including the solvent, passeshides and skins immersed therein will be difsumed, that a condition exists under which it will remaln neutral. My researches confirm the existence of such a state, and I h. vs taken the advantage to utilize such an action of the current, by means of special instruments, as a sterilizer for the arrest or prevention of the fermentation, which, under ordinary conditions would decompose the tannic acid and produce an economic loss or Waste.

The point of interest lies, however, in the fact, that adjustment of current density has an important effect as determining the character of the products as well as the chemical change that may take place throughout the I entire electrolyte. The electromotive force is dependent upon the density of the current employed, as well .as on the various resistances offered by reason of the differences in the quality of the hides or skins and the composition of the tannic liquor forming the electrolytic bath; these latter almost invariably decrease the resistance rapidly with rise of the temperature of the bath; and usually also with the composition, and especially the increased strength of the electrolytic tanning solution. Over-pressure will produce concentration of hydrogen ions; the potential difference at which hydrogen is de-' posited may vary considerably. The hydogen plays therefore an important role in electrotanning and its action is used by me as a safeguard in preventing the potential difference at the cathode from rising above a certain value. This value depends upon the concentration of the hydrogen ions and the overpressure, and is controlled in my system, by means of special instruments changing automatically the concentration of the hydrogen ions.

The preparation of the electrolytes, or the tanning liquors, is so far of importance as the tannins of the various tanning materials offer different resistances to the electric current, as do also the composition and concentration of the electrolytes, dependent, as I have discovered, to some extent upon the climatic conditions under which the tanning material has been cultivated. This should be considered in the preparation of the electrolytes, especially for concentrated mixed tannages.

The material employed for the electrodes as well as their construction will tend to affect the electrodic decomposition of tannin and should therefore be selected with a View to avoid loss of tannin.

The circulation of the electrolyte is an important factor, as with no circulation there would be no uniformity in the strength of the electrolytes, but injudicious agitation will cause loss of hide substance.

One is apt to overlook and forget these main points and fails therefore to see the necessity of due attention being given to them; this explains evidently the many failures experienced by those who have attempted to solve the important problem of electrotanning.

I prefer to employ electric energy both for electrolytic purpose and as motive power.

The current employed for electrolytic fpurpose in the tanks is preferably obtained rom a dynamo actuated by a motor, which is acted upon by the current from a main or otherwise, instead of being tapped direct from an existing main, by reason of the fluctuations of the load factor, and consequent unsteadiness of the pressure in the main. The current is first fed to a distribution board.

The density of the current is varied, and controlled in the usual way in accordance with the resistance of the electrolytes.

It is evident that the density needed for a proper electrotannage cannot be fixed beforehand: as little as one and the same remedy can cure all kinds of diseases: consequently, the operator must diagnose accord ing to circumstances and conditions. 'But generally speaking, for a battery of four tan pits, each filled with 50 hides, suspended in any tanning liquors of the strength of 4 degrees Baum, the density of current should not exceed ten amperes, while the pressure should be that needed to force the current of that density through the resistances offered by the hide and liquors in the tan pits, a pressure which does not exceed 120 volts.

The current used as motive power for operating the agitators is preferably generated by means of a semi-inclosed shuntwound-motor, which, while acted upon by the current from a main, or otherwise, is coupled to a set of worms and speed reducing gear, to reduce the speed of the motor to that required by the agitators.

The electrodes I prefer to make from perforated sheets or in strips of any suitable material, mounted on a wooden frame, which is placed on one side in the tank, its opposite side receiving the second electrode frame. These frames may be easily removed in case of need, without the necessity of emptying the tanks of the solutions they contain.

The electrical arrangements are fully illustrated in the drawings attached. The mechanical constructions needed in order to obtain the results desired are merely referred to, and insufficiently described in their details by reason of being subject matters for separate patents.

Figure 1. is a diagram of the electrical arrangements for a block of tanks divided into batteries of four tanks each.

Fig. 2. is likewise a diagrammatic plan, showing the connections of one complete circuit to one battery of four tanks.

Fig. 3. represents the distribution board for controlling the electricity for the tanks. Fig. 1. is a diagram of the electrical connections.

v Fig. 5. shows a three wire distribution board for controlling the motor.

Fig. 6. represents the electrodes.

Fig. 7. illustrates a diagram of agitators.

Figs. 8 and 9 illustrate a generating plant, mounted on one and the same bed plate.

The Figs. 1 to 9 are not drawn according to scale.

The motor-board K, (Figs. 1 and 2) has mounted thereon one ammeter G, one double pole combined twin-break switch and fuse W, and one double semi-inclosed motor starter U, having no-volt and overload release.

The generator board I, (Figs. 1 and 2) has mounted thereon an ammeter G, one

volt meter H, one double pole change-over quick-break knife-switch S, two single pole fuses F, and one regulator V.

The block A of tanks, (Figs. 1 and 2) divided in batteries B of four tanks are connected in series with circuits C, the circuit C being a negative return lead-wire common for all batteries. D represents the distribution board, I the generator board; M the generator, P the motor with motor board K, and connections N with the main supply.

The distribution board D for the central of, for instance, four batteries of four tanks, each in series, as illustrated in Figs. 3 and 1, requires for each battery the following instruments and devices One single pole automatic circuit breaker 0, one ammeter G, one single pole fuse F to prevent overload, one alarm voltmeter H, which automatically opens the circuit in the event of the concentration of the hydrogen ions rising beyond the predetermined amount for the respective tanks, each being provided with a safety density indicating lamp L, with fuse F, one single pole switch S, and one reversing single pole switch 8" and voltmeter switch S, N being the distribution bars (Figs. 1, 2 and 4) all connected in the usual way. The switches S" and 8" may be substituted for one double pole reversing switch, as may also the four ammeters be substituted for one, the connections being modified accordingly. The reference letter R designates resilient coils usually variable, as clearly indicated in Fig. 2.

The three wire distribution board, for controlling the motor P shown in diagram in Figs. 2 and 5, is provided with a starter U, one double pole switch W, and two single pole fuses F, and the'shunt regulator Z.

The anodes E and cathodes E, shown in detail in Fig. 6, are mounted on the wooden frames 6.

The agitators, Fig. ment on those formerly used in the art, as each battery T, divided from the adjacent batteries by the partitions 25, requires only one wooden frame to carry the hides; and each of which frames is provided with a driving-rod r, the other end of which is hook-shaped so as to be easily dropped on or lifted up from the cranks C, of the agitating crank shaft S nected with the crank d, on the worm and speed gearing WS' while 9 represents the bearings for such shaft.

Each battery is thus being worked independently from the other, and being automatic in its working it requires no special attention. v

The generating lant is shown in Figs. 7, 8 and 9, wherein is the motor, connected on one side with the worm and speed gearing WS, the crank 01, of which is coupled at one end direct to the crank shaft 8*, and on its other end to the generator M.

The moclus opemmii is generally as follows: a

The hides or skins are suspended in the tanks containing aqueous solutions of the ordinary ingredients used in the various processes prior to, and during the tannage, and kept there together with the respective solutions, by means of the agitating power, in edgewise and reversing horizontal motion continually remaining in the solution in con tradistinction to a vertical or combined vertical and horizontal or pendular direction, or equivalent motion, whereby the hides or skins are constantly being lifted out of the solution, and thereby exposed to the injurious action of the oxygen of the air, preventing also thereby a uniform tannage, While an electric current is forced through the liquors and the hides orskins, in order to accelerate and perfect the respective processes. For instance, the actual time of a tannage of a lbs. fresh market hide for sole leather is 4 weeks; two additional weeks are needed, one for preparing the hides, and one for finishing the leather produced.

As indicated in Figs. 1 and 7, there are six separate and distinct tan-pits, arranged 7, are a great improvethe hides or skins so (Fig. 7), which is con-.

usually in line, and in my improved process the hides or skins to be treated are immersed one Week in each of such tan-pits or tanks; and. are weekly transferred from tank to tanli successively, from the first to the sixth of such tan-pits or tanks, and the last of i which having been completely tanned and fully treated they are removed and made ready for the market.

The operation or method of carrying my improved process into effect is substantially as follows:

All the tanks are first primed and filled With the proper liquids for each successive different process, and during the first week the first pack of hides are placed in tank 1, and given one weeks treatment. At the end of such first'week, such pack of hides is shifted to the second adjacent tank and treated for a week, and so on successively, tanned and treated are shifted from tank to tank until, at the end of the treatment in the last and sixth tank, they are fully finished, tanned and ready to be taken out, dried, and put upon the market.

The tannage may be continued day and night, and the electric current applied according to circumstances. The manual labor needed for every 400 hides during the tan nage proper is two lads, whocan also manipulate the electric plant, and have also time to prepare the tanning liquors. The motive power is 2 H. P. for every 200 hides.

Observations during many years of research and costly experiments, not merely in the laboratory, but more often upon a com mercial basis with packs of hides, and skins, necessitating also the consideration, even of the smallest detail, as all of them oflered difiiculties of more or less severe nature, have enabled me to simplify my former system of electrotanning by dispensing with all the usual lime-pits, color pits, handlers, and layers, using only a small number of suspender pits, with a fewsoaks admitting of any blend or mixture of tanning material being employed, with a finishing strength of about one-tenth of that generally used, and equally applicable to all kinds of leathers; for vegetable or mineral tannages, or for a combination of both, resulting in the reduction of the time of tannage to one-sixteenth; the working capital by 80 per cent, and the cost of production by 50 per cent, While the quality of the leather is unsurpassed by reason of its uniform tannage: and as the tanning process is almost automatic in its working, great economic results are obtained.

Having now particularly described and ascertained the nature of my invention, and in what manner the same is to be performed, I would have it understood that I do not claim broadly the use of electricity in tanning, or apparatus for keeping the hides,

skins and tanning liquors in motion, nor do I limit myself to the exact strength of configuration of the parts I have explained and shown, but I declare that What I do claim 1s:

1. In an apparatus for tanning hides or skins, means forsuspending the hides or skins in a frame or frames in a tannic electroconductive bath of liquid; horizontally agitating the frame or frames; and automatically varying the density or amperage or pressure or voltage of the current transmitted through the bath according to the conditions obtaining within the bath at the moment, While maintaining the hides or skins immersed in the bath; theelectrolytic ta'nnic bath being divided into a plurality of baths; means for moving the hides or skins in the electrolytic-bath in the plane of such skins or hides while immersed in the liquor; and means for automatically varying the amperage or density, or the pressure or voltage of the current passing through each individual bath of the battery of baths, according to the electrolytic condition obtairiling at the moment in such individual bat 2. The hereinbefore described method of tanning hides and skins, comprising the following steps (1) immersing the same in an electrolytic-bath, for a suitable period during current action; (2) placing the hides or skins in a second electrolytic-bath, and inserting untreated hides or skins in the first-bath, and submitting the skins in the two baths to like treatment for a like synchronous period; (3) shifting the hides or skins again in like manner, and inserting a fresh lot in the first-bath, and repeating the treatment; (at) again shifting the hides or skins and inserting afresh lot in the first bath, and repeating the treatment, and (5) removing the lot in the fourth bath, shifting, adding a fresh lot to the first bath, and again simultaneously treating, and so continuing.

3. The hereinbefore described method of tanning hides and skins, comprising the following steps (1) immersing the same in an electrolytic-bath, for a suitable period during current action; (2) placing the hides or skins in a second electrolytic-bath, and

inserting untreated hides or skins in the first-bath, and submitting the skins in the two baths to like treatment for a like synchronous period; (3) shifting the hides or skins in a like manner, and inserting a fresh lot in the first-bath, and repeating the treatment; (4) again shifting the hides or skins and inserting a fresh and repeating the treatment, and (5) removing a lot in the first bath,

the lot in the fourth bath, shifting, add-- fresh lot to the first bath, and again treating, and so continuing;

each bath being of difing simultaneously treating liquor in ferent composition.

4. The hereinbefore described tanning hides and skins, comprising the following steps (1) immersing the same in an electrolytic-bath, for a suitable period during current action; (2) placing the hides or skins in a second electrolytic-bath, and inserting untreated hides or skins in the first-bath, and submitting the skins in the two baths to like treatment for a like synchronous period; (3) shifting the hides or skins again in like manner, and inserting a fresh lot in the first bath, and repeating the treatment; (4:) again shifting the hides or skins and inserting a fresh lot in the first bath, and repeating the treatment, and (5) removing the lot in the fourth bath, shifting, adding a fresh lot to the first bath, and again simultaneously treating, and so continuing; treating liquor in each bath being of different composition; and the character of the electric current passing through each bath being different.

5. The hereinbefore described method of tanning hides and skins, comprising the following steps (1) immersing the same in an electrolytic-bath, for a suitable period during current action; (2) placing the hides or skins in a second electrolytic-bath, and inserting untreated hides-or skins in the first-bath, and submitting the skins in the two baths to like'treatment for a like synchronous period; (3) shifting the hides or skins in a like manner, and inserting a fresh lot in the firstbath, and repeating the treatment; (4) again shifting the hidesor skins and inserting a fresh lot in the first bath, and repeating the treatment, and (5) removing the lot in the fourth bath, shifting, adding a fresh lot to the first bath, and again simultaneously treating, and so continuing; treating liquor in each bath being of different composition; the character of the electric current passing through each bath being different; and being automatically varied according to the conditions at the moment obtaining within such particular individual bath.

In testimony that I claim the foregoing as my invention I have signed my name in the presence of two subscribing witnesses.

LORENTZ ALBERT GROTH.

Witnesses:

O. J. WORTH, R. WILLIAMS.

method of, 

